(1) Field of the Invention
The present invention relates to a workpiece feeder and, more particularly, to an apparatus for feeding workpieces to a workpiece gripping position of a hand of an industrial robot.
(2) Description of the Prior Art
In fully automated factories, industrial robots are used for loading and unloading workpieces on and from lathes, milling machines, drilling machines, and other machine tools. Industrial robots are served by workpiece feeders which feed workpieces one by one to workpiece gripping position of the industrial robot. A known workpiece feeder includes a frame, a table mounted on said frame, and an endless conveyor mounted on said table. The conveyor of the workpiece feeder comprises an endless linkbelt having at least one belt run portion extending over said table. A plurality of pallets interspaced from each other at equal distances are connected to the linkbelt in such a manner that they are moved along a predetermined path extending across a point located below the gripping station of the hand of the robot. The conveyor is driven intermittently so that each of the pallets is successively brought under the gripping station of the robot and is held in place for the time period required for the robot to grip the workpiece on the pallet and load it on a machine tool for machining thereof. After machining, the robot unloads the workpiece from the machine tool and places it back on the workpiece feeder or transfers it to another workpiece feeder serving another robot associated with another machine tool.
In its normal form, an industrial robot has a base on which an upright stand is swiveled for rotation about a vertical axis. The upright stand comprises a lead screw and a pair of opposite parallel guide shafts on which a carriage is mounted for vertical translational movement. The carriage is provided with a horizontal telescoping arm, at the free end of which is mounted a robot hand by means of a wrist which enables the hand to rotate about a horizontal axis as well as to swing about a vertical axis. The horizontal telescoping movement of the arm in combination with the vertical translational movement of the carriage and swivelling motion of the upright stand enables the robot hand to move toward any desired three-dimensional point within the reach of the arm and to grip a workpiece placed on a pallet of the conveyor located at any three-dimensional position.
However, the above-mentioned three dimensional-type robots suffer from high production costs. Industrial robots simpler in construction, i.e., not having the upright stand, have therefore been developed and have come into wide use. Such simplified robots have telescoping arms mounted on arm holders which, in turn, are hinged to a bracket mounted rotatably on a base about a horizontal axis. Thus, the robot's hand is only capable of gripping workpieces positioned at a predetermined height. In order to ensure the robot hand correctly grips a workpiece, the workpiece must first be elevated to the height of the gripping position of the hand. As of now, there have been no workpiece feeders able to be used for such simplified industrial robots.